<?php
//变量的类型
$a = 123;
$b = '456';
$c = true;
$d = [];
$e = 3.14;
var_dump(is_int($a));
var_dump(is_int($b));
var_dump(is_string($b));
var_dump(is_bool($c));
var_dump(is_array($d));
var_dump(is_float($e));
echo "---------------\n";
$arr = [123, '456', true, [], 3.14];
foreach ($arr as $k => $v) {
    echo "$k. ", gettype($v), "\n";
}